During the current year, 650 hemagglutination inhibition tests for CEA were carried out on sera obtained from 562 individuals. In patients with known colonrectal cancer, 65% of the tests were positive. In 10.4% of control patients, without known gastrointestinal disease, positive tests were also obtained; as well as in 22% and 38% of patients with benign gastrointestinal and liver disease respectively. Preliminary tests indicate that a four hour period of preliminary dialysis of perchloric acid treated serum is as satisfactory as 72 hour dialysis. Three fractions of molecular weight, 200,000, 70,000 and 60,000, have been obtained from CEA extracts by polyacrylamide gel electrophoresis after eluting the material from affinity columns. During the next grant year, the comparison of four hour vs 72 hour dialysis tests will be completed. Fetal tissues will be used to absorb antisera in an attempt to render it monospecific. The physicochemical and immunological properties of the three molecular weight CEA materials will be characterized.